Objectives: 

The purpose of our study was to measure the effects of acute and chronic exercise on cell and mitochondrial membrane fluidity from rat skeletal and cardiac muscles, and to compare the fluidity levels of exercised vs. control rats.

Materials: 

50 male Sprague-Dawley rats (250 ± 25 g) were distributed into 5 groups (n=10/group) depending on exercise protocol: acute exercise, 1 week training, 4 weeks training and 12 weeks training. One group acted as control. Excepting Control group, all rats were subjected to a progressive acute test until exhaustion in a treadmill. With this acute exercise, workloads % were determined for training groups, attending at the maximum speed achieved. Training sessions were intervallic, alternating 80% and 35% of workload, 1 h/day, 4 days/week. Skeletal muscle and heart were removed, and their cell and mitochondrial membranes were isolated by differential centrifugation. Fluidity was determined by fluorescence spectroscopy, using TMA-DPH as fluorescent probe, and it was expressed as the inverse of polarization measured (1/P).

Results: 

Acute and training-chronic exercise decreased cell membrane fluidity levels in skeletal muscle compared with control, being significant in all of them (excepting 1 week training). Related to skeletal muscle mitochondrial membranes, a significant decrease in the fluidity levels in all exercise groups was clearly observed. Also, in cardiac muscle there was an increased rigidity too, both in cell and mitochondrial membranes, after performing different exercise protocols in comparison to control. All changes were significant.

Conclusions: 

These results suggest that exercise, independently of its duration or intensity, induces a severe rigidity on cell and mitochondrial membranes in rat skeletal and cardiac muscles, producing structural alterations and affecting its dynamics. These changes may be consequence of an increase in mitochondrial activity due to exercise, which could lead to a higher free radical formation resulting in oxidative damage.